This invention relates generally to seals, and more particularly to an automatic sequential dual action sealing system especially useful in a shock absorbing subassembly used in a downhole oil well drilling.
Shock absorbing subassemblies, such as that disclosed in U.S. Pat. No. 3,406,537 issued to C. B. Falkner, Jr. on Oct. 22, 1968, have been used for many years to absorb shock and vibration between a drill bit and a drill string. However, such shock absorbing subassemblies have been limited insofar as the pressure of the drilling fluid is concerned and insofar as their useful lives are concerned, both limitations being due at least in part to the sealing systems heretofore used. The present invention which arose in the context of the need for a better sealing system in a downhole tool, particularly a shock absorbing subassembly requiring a high pressure seal between telescoping male and female cylindrical members which undergo limited relative axial movement, is not limited to such applications; rather, it is useful in providing an effective seal between male and female cylindrical members in general.
Dual seals per se have been disclosed in U.S. Pat. Nos. 3,588,124 and 3,776,588. However, the first of those is not automatic, and the second requires very complex structure. The present invention provides a simple automatic sequential dual action sealing system. Other references of general interest for background purposes are U.S. Pat. Nos. 2,786,534, 3,504,936, 3,752,507, and 3,807,513.